1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, an in-plane switching mode liquid crystal display device.
2. Discussion of the Related Art
Twisted nematic liquid crystal display devices (hereinafter TN LCDs) having high image quality and low power consumption are widely applied to flat panel display devices. TN LCDs, however, have a narrow viewing angle due to refractive anisotropy of liquid crystal molecules. This is because horizontally aligned liquid crystal molecules prior to applying a voltage become nearly vertically aligned with respect to the substrate when voltage is applied to the liquid crystal panel.
Recently, in-plane switching mode liquid crystal display devices (hereinafter IPS-LCDs) have been widely studied for improving the viewing angle characteristic. These liquid crystal molecules are nearly horizontally aligned.
FIG. 1a is a plan view of a unit pixel of a conventional active matrix LCD. As shown in FIG. 1a, unit pixel region is defined by a gate bus line 1 and a data bus line 2 in which the lines 1, 2 are arranged perpendicularly and/or horizontally in a matrix on a transparent substrate (first substrate) 10. A common line 3 is arranged parallel to the gate bus line 1 in the pixel region. A thin film transistor (TFT) is formed adjacent a cross point of the data bus line 2 and the gate bus line 1. The TFT, as shown in FIG. 1b which is a sectional view according to line Ixe2x80x94I of FIG. 1a, includes a gate electrode 5, a gate insulator 12, a semiconductor layer 15, a channel layer 16, and source/drain electrode 6. The gate electrode S is connected to the gate bus line 1 and source/drain electrode 6 is connected to the data bus line 2. The gate insulator 12 is formed on the whole surface of the first substrate of the first substrate 10.
A common electrode 9 and a data electrode 8 are formed in the pixel region. The common electrode 9 is formed with the gate electrode 5 and connected to the common line 3. The date electrode 8 is formed with the source/drain electrode 6 and electrically connected to the source/drain electrode 6. Further, a passivation layer 20 and a first alignment layer 23a are deposited on the whole surface of the first substrate 10.
On a second substrate 11, a black matrix 28 is formed to prevent a light leakage which is generated around the TFT, the gate bus line 1, and the data bus line 2. A color filter layer 29, and a second alignment layer 23b is formed on the black matrix 28 in sequence. Also, a liquid crystal layer 30 is formed between the first and second substrates 10, 11.
When voltage is not applied to the LCD having the above structure, liquid crystal molecules in the liquid crystal layer 30 are aligned according to alignment directions of the first and second alignment layers 23a, 23b. However, when voltage is applied between the common electrode 9 and the data electrode 8, the liquid crystal molecules are vertically aligned to the extending directions of the common and data electrodes. In the foregoing, since liquid crystal molecules in the liquid crystal layer 30 are switched on the same plane at all times, grey inversion is not created in the up and down direction, and right and left direction of the viewing angle.
In the conventional LCD having the above structure, however, the aperture ratio is decreased by the data electrode 8 and the common electrode 9, which are opaque.
Accordingly, the present invention is directed to an in-plane switching mode liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an LCD having a high aperture ratio.
Another object of the present invention is to provide an LCD having a light transmissive common and data electrodes.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an in-plane switching mode liquid crystal display device comprises first and second substrates; a plurality of gate and data bus lines defining pixel regions and arranged on said first substrate; a plurality of thin film transistors adjacent respective cross points of said gate and data bus lines; a plurality of gate electrodes connected to said gate bus lines; a gate insulator on said gate electrodes; a first metal layer including a plurality of first electrodes on said gate insulator; a passivation layer on said first metal layer; and a transparent second metal layer including a plurality of second electrodes on said passivation layer, wherein said first and second electrodes apply plane electric fields.
In another aspect of the present invention, an in-plane switching mode liquid crystal display device comprises a thin film transistor on a substrate including source, drain, and gate electrodes; a data electrode connected to one of the source and drain electrodes; and a common electrode, wherein the data electrode, the common electrode, and the gate electrode are each on different layers over the substrate.
In another aspect of the present invention, an in-plane switching mode liquid crystal display device comprises a substrate; a thin film transistor including source, drain, and gate electrodes on a portion of the substrate; a first insulating layer on the substrate; a first electrode including a data electrode on the insulating layer; a second insulating layer covering the first electrode; and a second electrode including a common electrode on the second insulating layer, wherein the gate electrode, the first electrode, and the second electrode are on different layers.
In another aspect of the present invention, a method of forming an in-plane switching mode liquid crystal display device comprises the steps of forming a thin film transistor on a substrate including source, drain, and gate electrodes; forming a data electrode connected to one of the source and drain electrodes; and forming a common electrode, wherein the data electrode, the common electrode, and the gate electrode are each on different layers over the substrate.
In a further aspect of the present invention, a method for forming an in-plane switching mode liquid crystal display device comprises the steps of forming a thin film transistor including source, drain, and gate electrodes on a portion of a substrate; forming a first insulating layer on the substrate; forming a first electrode including a data electrode on the insulating layer; forming a second insulating layer covering the first electrode; and forming a second electrode including a common electrode on the second insulating layer, wherein the gate electrode, the first electrode, and the second electrode are on different layers.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.